Volume 26 (2018): Issue 4 (December 2018)

Wooden trusses are a very specific object for measurement. They are often very complex and hard to reach; they are characterized by narrow spaces and low-lighting conditions. In recent years, laser scanning technology was mostly used for this task, because of its contactless nature, the possibility of measurement in the dark, and the robustness of the resulting 3D point clouds. Photogrammetry was mostly used in special cases, e.g., for the measurement of a few selected truss components, but not for the 3D modelling of an entire truss. However, the progress in computer vision algorithms is allowing us to accomplish image-based-modelling on very complex objects. The following contribution compares the point clouds of a wooden truss generated by the leading photogrammetry systems with a point cloud from laser scanning. The results confirm the interesting potential of actual photogrammetric methods in the modelling of complex objects such as wooden trusses.

The article is focused on a regression analysis of small strain shear and constrained modulus measurements of 15 different natural sands with plastic fines from the Pannonian basin. Measurements done within this work are supported by additional data on sands with plastic and non-plastic fines gathered from the literature in order to demonstrate the versatility of the approaches used and behavior observed. Bender / extender element techniques are used in this study for measuring the small strain shear and constrained modulus of sands with fines. Three void ratio functions, which are commonly used in predictive empirical equations for predicting small strain stiffness, with corresponding fitted parameters are presented, and their effect on the accuracy of the regression procedure is studied. It is assumed that all the void ratio functions tested provide nearly the same degree of accuracy and that the fitted models are able to predict the values of the parameters measured within an acceptable range of errors. Finally, proposed constant regression constants for sands with plastic fines are given.

Crushed Stone Dust (CSD), which is a waste product from an aggregate crusher, could be used as a pavement layer. To improve the tensile strength of CSD, it is worthwhile reinforcing it. In the present study an attempt has been made to reinforce a loosely and densely compacted CSD layer with Hexagonal Wire Mesh (HWM) placed in various positions. The results indicate that the California Bearing Ratio (CBR) value is improved by the placement of HWM in CSD. Field Rutting studies were also conducted on test tracks made of unreinforced and reinforced CSD layers. The rut depths were significantly reduced due to the inclusion of the reinforcement in the CSD layer.

Residential kitchens with gas stoves are unique spaces inside dwellings.Occupants directly exposed to the combustion products and thermal effects of the stove. Applying a general model with the knowledge of describing parameters, designer could taken thermal aspects also into consideration in order to provide a save, healthy and comfortable environment in residential kitchens and homes. The aim of this study to develop this model and a new ventilation method. Results of field studies shows disadvantageous effect of kitchen exhaust unit during the operation of oven. However turbulence intensity was decreased from 123% to 25% , indoor temperature was increased by 3,7K in the occupied zone due to the forced air movement. PMV index remained within the recommended intervals (between -1,0 and +1.9), therefore it could be applied to evaulate thermal environment aroun the residential gas stove. Unpleasent effect of draught is not expected.

The paper presents an adapted methodology of laser holographic interferometry for an investigation of the stress-strain state of nailed timber connections. During the study the possibility of detecting local deformations in the connection were verified. The optimum conditions for fixing the samples and the loading ranges to ensure an optimal interference pattern were determined. An investigation of the peculiarities of the interaction between the elements and the stress-strain behavior of nailed timber connections was performed. The experimental data obtained on the stress-strain behavior of a nailed timber connection using the laser holographic interferometry method have sufficient repeatability between different series and can also be used as a criterion verification for a finite-element model.

The European standard for the design of concrete structures using nonlinear methods contains a deficit in global reliability for cases when concrete columns fail due to a loss of stability before reaching the design resistance in the critical cross-sections. A buckling failure is a brittle failure which occurs without warning, and the probability of its formation is markedly influenced by the slenderness of the column. The calculation results presented herein are compared with the results from experimental data. The paper aims to compare the global reliability of slender concrete columns with a slenderness of 90 and higher. The columns are designed according to the methods stated in EN 1992-1-1, namely, a general nonlinear method and methods based on nominal stiffness and nominal curvature. The mentioned experiments also served, on the one hand, as a basis for the deterministic nonlinear modeling of the columns and, subsequently, for the probabilistic evaluation of the variability of the structural response. Finally, the results may be utilized as thresholds for the loading of the structural elements produced. The paper aims at presenting a probabilistic design that is less conservative than the classic partial safety factor-based design and alternative ECOV method.

Municipalities have a great deal of interest in land consolidation. Deciding which municipality is going to be prioritized for land consolidation is not easy; a unified universal selection procedure does not currently exist. The article proposes a procedure for assessing land ownership in a municipality. Municipalities with the worst ratings should be prioritized for land consolidation. The selection of evaluation parameters and their classification into groups is the result of previous experience. The parameters cover a broad spectrum of variables, economic conditions, the spatial structure of the agricultural land, the fragmentation of land and land ownership, the ecological stability of the land, territorial endangerment as well as natural conditions, technical limitations, and other regional specifics. The proposed quantification of the status of real property can be used with the aim of prioritizing municipalities, even with a variable number of evaluation parameters. To test the proposed algorithm, analyses were carried out in three municipalities located in west Slovakia. The municipalities were ranked according to the need to perform land consolidation

The Muskingum method is based on a linear relationship between a channel’s storage and inflow and outflow discharges. The applicability of using travel-time discharge relationships to model the variability of the K parameter in a Muskingum routing model was tested. The new parameter estimation method is based on the relationships between the traveltime parameter (K) and the input discharge for the reach of the Danube River between Devín-Bratislava and Medveďov, which includes the Gabčíkovo hydropower scheme. The variable parametrisation method was compared with the classical approach. The parameter X was taken as the average of its values from a small set of flood waves, K was estimated as a function of the travel-time parameter and discharge, which was optimized for one flood wave. The results were validated using the Nash-Sutcliffe coefficient on 5 floods. The results obtained by these methods were satisfactory and, with their use, one could reduce the amount of data required for calibration in practical applications.

The article documents the development of a modular transparent elemental facade. The cooperative development was realized in two areas, i.e., the development of facade ventilation units for an under-pressure ventilation system and experimental verification in a laboratory of a facade panel and optimization of its acoustic parameters. The task of controlled ventilation in modern residential buildings is to ensure the optimum quality of the interior environment and fulfill hygienic and thermal technical requirements that guarantee the comfort of the users. The paper discusses the development and experimental verification of atypical vertical ventilation units of an under-pressure controlled ventilation system for a residential high-rise building. A recommended concept for the facade´s details has been developed in relation to the ventilation system. Conceptual designs of alternatives to the air inlet openings of an under-pressure controlled ventilation system for the apartments with an atypical vertical geometry were proposed. An optimized alternative to air inlet openings in the bottom level of a vertical pilaster with the function of an air distribution channel for a ventilation system has been selected and developed. Laboratory experiments have verified the physical properties of the optimized alternative ventilation units of the under-pressure controlled ventilation system in their development cycle. The hydrodynamic regime of the air inlet openings of the controlled ventilation system has been verified by experimental research in a laboratory large rain chamber. The aerodynamic regime of a naturally controlled ventilation system was verified by experimental research in a large laboratory pressure chamber. The acoustic properties of the naturally controlled ventilation system were verified by experimental research in a laboratory´s acoustic chambers. The verified parameters of the ventilation units of the under-pressure controlled ventilation obtained by the experiment were compared with the design parameters. An experimental assessment of the mechanical, thermal and acoustical parameters of the elemental modular facade was carried out in a laboratory. At the end of the article, the results and conclusions of the laboratory experiment are summarized.

In this research, a combined method was developed to determine the erodibility of bends in the Karkheh River. For this purpose, a 40 km reach of the Karkheh River downstream of the Karkheh Dam was considered. The value of the shear stress was the calculated using the CCHE2D model. The results from the model show that in 1996 (before construction of the Karkheh dam), the length of the erodible reach was 1314 m; in 2011 (after construction of the Karkheh dam), this length was reduced to 840 m. Furthermore, the model illustrates that the location of the maximum shear stress is a function of the relative curvature (R/W) in the bends. For small values of the R/W (less than 1.5), the maximum shear stress occurs on the convex bank of a river bend. By increasing the R/W, the location of the maximum shear stress transfers to the concave bank of the river bend. Also, this location is displaced towards downstream by increasing the R/W.